Coextruded polylactide/encapsulated cinnamon essential oil/graphene nanoplatelets trilayer films: Morphological, barrier, thermal, rheological and antimicrobial properties

Polylactide (PLA)-based biodegradable three-layer packaging film was fabricated using PLA, PLA/cinnamon oil (CEO), and PLA/graphene nanoplatelets (GNP). The central layer allows control over the release of antimicrobes, and the outer layer adds mechanical strength to the films. A comparison has been made on barrier, thermal, rheological, microstructural, and microbiological properties between single-layer and multilayer films (MLF). The water vapor and oxygen barrier properties of MLF showed little reduction compared with those of neat PLA. The tensile stress of the neat PLA increased significantly from 23.31 to 35.91 MPa for the MLF. Thermal analysis data showed improvements in the thermal stability of the MLF film, with onset and peak temperatures of 331.5 and 357.1°C, respectively. The dispersion of GNP in the PLA matrix and in MLF was assessed by XRD analysis and rheological measurement. The AFM roughness parameters Sa and Sq of those films varied widely, with the highest (13.9 and 20.9 μm) and the lowest (0.08 and 0.11 μm) magnitudes recorded for PLA/GNP and PLA/CEO films, respectively. Antibacterial assays of the film confirmed a strong bactericidal effect against Listeria monocytogenes and Salmonella typhimurium, maintaining this activity for 21 days. Highlights: Polylactide/cinnamon oil/ graphene nanoplatelet multilayer films were coextruded. X-ray diffraction and rheology confirm the dispersion of graphene into PLA. Tensile stress and thermal stability improved in the multilayer films. AFM roughness parameters varied significantly between single- and multilayer films. Antibacterial assays confirmed the strong bactericidal effect of films against pathogens.